The invention is concerned with an extensible weight compensating apparatus or balancer for compensating for the weight of a tool such as an assembly tool as may be used for example on an assembly line in a factory.
Weight compensating means, also often referred to as balancers, are used as an assistance in making the work of an operator easier in carrying out production and machining operations involving the use of manually guided tools such as drilling or boring machines, grinding machines, screwing machines such as bolt and screw drivers, spot-welding tongs, riveting hammers, stirring mechanisms and the like. The balancers operate in such a way that a spring such as a coil spring, which is under a prestress corresponding to the weight of the tool, holds in a condition of equilibrium or balance the load of the tool, which thus applies a force to a cable drum by means of cable from which the tool is hung. By hanging the tools on a balancer of this kind, the weight of the tool is virtually nullified. However, with the known balancers, the tools are fully balanced in this way only within a given range of tool movement from the rest position of the tool and thus within a given range of extension of the cable, being the range within which the weight of the tool is in equilibrium with the spring force acting on the cable. Under different conditions in respect of the length of cable extension, the spring force of the mechanical spring alters, and a satisfactory weight balancing action is achieved only within a relatively small range of movement. The known balancers must therefore be adapted to the specific tool which is to be connected thereto and thus balanced thereby. Therefore, for different tools, in particular for tools of different weights, it is necessary to provide a number of balancers which are of different designs which thus provide different spring balancing actions. In addition, the length by which the tool may be extended or displaced from a rest position is also limited, in dependence on the spring used, for the reasons already referred to above. In addition, manually operated tools, for example screwing means, produce forces, in the course of operation, which must be resisted by the muscle power of the operator, when using the known balancers. In this respect therefore, the known balancers do not give full satisfaction in regard to making the work of the tool operator easier.